Electronic Device With Ambient Light Sensor System

ABSTRACT

An electronic device may be provided with a display mounted in a housing. Color ambient light sensors may make measurements of ambient light intensity and color through windows in an inactive border region of the display or other portions of the device. The electronic device may process the ambient light measurements based on ambient light information from the ambient light sensors and based on information from additional sensors such as an image sensor, a force sensor, a capacitive touch sensor, a proximity sensor, an orientation sensor, and other devices. Control circuitry in the electronic device may produce reliable ambient light measurements by combining readings from multiple reliable sources and by discarding readings from ambient light sensors that are blocked by a user&#39;s fingers or other external objects. Display color cast and intensity may be adjusted based on ambient light information.

This application claims the benefit of provisional patent applicationNo. 62/291,375, filed Feb. 4, 2016, which is hereby incorporated byreference herein in its entirety.

BACKGROUND

This relates generally to electronic devices, and, more particularly, tolight sensors for electronic devices.

Electronic devices such as laptop computers, cellular telephones, andother equipment are sometimes provided with light sensors. For example,ambient light sensors may be incorporated into a device to provide thedevice with information on current lighting conditions. Ambient lightreadings may be used in controlling the device. If, for example brightdaylight conditions are detected, an electronic device may increasedisplay brightness to compensate.

Ambient light sensors can sometimes produce erroneous readings. Forexample, a user's finger or other external object may block an ambientlight sensor. In this type of situation, the ambient light sensor mayproduce a reading that does not accurately reflect ambient lightingconditions. If care is not taken, this may lead to inappropriate displayadjustments.

It would therefore be desirable to be able to provide improved systemsfor sensing ambient light in electronic devices.

SUMMARY

An electronic device may be provided with a display. Color ambient lightsensors may make measurements of ambient light intensity and colorthrough windows in an inactive border region of the display. An imagesensor may be located under a display window that is located between thewindows associated with the color ambient light sensors. Additionalsensors may also be used.

The electronic device may process ambient light measurements to producereliable ambient light information. Ambient light measurements may beprocessed based on ambient light information from the ambient lightsensors and based on information from additional sensors. Historicalambient light sensor data and predetermined performance criteria canalso be used in processing ambient light sensor measurements. Theadditional sensors that are used in supplying this information mayinclude the image sensor located under the display window and/or otherimage sensors, force sensors, capacitive touch sensors, proximitysensors, orientation sensors, and/or other input-output devices.

Control circuitry in the electronic device may produce ambient lightmeasurement by combining readings from multiple reliable sources and bydiscarding readings from ambient light sensors that are blocked by auser's fingers or other external objects. Display color cast andintensity may be adjusted based on ambient light information.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an illustrative electronic device inaccordance with an embodiment.

FIG. 2 is a front perspective view of a portion of an illustrativeelectronic device in accordance with an embodiment.

FIG. 3 is a rear perspective view of the illustrative electronic deviceof FIG. 2 in accordance with an embodiment.

FIG. 4 is a cross-sectional side view of an illustrative light sensormounted under a window in an inactive portion of a display in accordancewith an embodiment.

FIG. 5 is a top view of an illustrative ambient light sensor showing howan adjacent proximity sensor and overlapping touch sensor may beprovided to monitor for objects in the vicinity of the ambient lightsensor in accordance with an embodiment.

FIG. 6 is a flow chart of illustrative operations involved in processingambient light sensor signals in accordance with an embodiment.

FIG. 7 is a flow chart of illustrative operations involved in usingimage sensor information in the processing of ambient light sensorsignals in accordance with an embodiment.

FIG. 8 is a diagram showing how information from sensors and otherinput-output devices may be used in processing ambient light sensor datain accordance with an embodiment.

FIG. 9 is a flow chart of illustrative steps involved in usinginformation from input-output devices such as sensors in processingambient light sensor signals in accordance with an embodiment.

DETAILED DESCRIPTION

An illustrative electronic device of the type that may be provided withone or more light sensors is shown in FIG. 1. Electronic device 10 maybe a computing device such as a laptop computer, a computer monitorcontaining an embedded computer, a tablet computer, a cellulartelephone, a media player, or other handheld or portable electronicdevice, a smaller device such as a wrist-watch device, a pendant device,a headphone or earpiece device, a device embedded in eyeglasses or otherequipment worn on a user's head, or other wearable or miniature device,a television, a computer display that does not contain an embeddedcomputer, a gaming device, a navigation device, an embedded system suchas a system in which electronic equipment with a display is mounted in akiosk or automobile, equipment that implements the functionality of twoor more of these devices, or other electronic equipment.

As shown in FIG. 1, electronic device 10 may have control circuitry 16.Control circuitry 16 may include storage and processing circuitry forsupporting the operation of device 10. The storage and processingcircuitry may include storage such as hard disk drive storage,nonvolatile memory (e.g., flash memory or otherelectrically-programmable-read-only memory configured to form a solidstate drive), volatile memory (e.g., static or dynamicrandom-access-memory), etc. Processing circuitry in control circuitry 16may be used to control the operation of device 10. The processingcircuitry may be based on one or more microprocessors, microcontrollers,digital signal processors, baseband processors, power management units,audio chips, application specific integrated circuits, etc.

Input-output circuitry in device 10 such as input-output devices 12 maybe used to allow data to be supplied to device 10 and to allow data tobe provided from device 10 to external devices. Input-output devices 12may include buttons, joysticks, scrolling wheels, touch pads, key pads,keyboards, microphones, speakers, tone generators, vibrators, cameras,light-emitting diodes and other status indicators, data ports, etc. Auser can control the operation of device 10 by supplying commandsthrough input-output devices 12 and may receive status information andother output from device 10 using the output resources of input-outputdevices 12.

Input-output devices 12 may include one or more displays such as display14. Display 14 may be a touch screen display that includes a touchsensor for gathering touch input from a user or display 14 may beinsensitive to touch. A touch sensor for display 14 may be based on anarray of capacitive touch sensor electrodes, acoustic touch sensorstructures, resistive touch components, force-based touch sensorstructures, a light-based touch sensor, or other suitable touch sensorarrangements.

Input-output devices 12 may also include sensors 18. Sensors 18 mayinclude ambient light sensors such as color ambient light sensors 20,orientations sensors 22 (e.g., accelerometers, compasses, motionsensors, gyroscopes, etc.), proximity sensors 24, touch sensors 26,force sensors 28, and image sensors 30.

Ambient light sensors 20 may be used to make ambient light intensity(brightness) measurements. Ambient light intensity measurements, whichmay sometimes be referred to as ambient light luminance measurements,may be used by device 10 to adjust display brightness (as an example).Ambient light sensors 20 may be used to make measurements of ambientlight color (e.g., color coordinates, correlated color temperature, orother color parameters representing ambient light color). Ambient lightcolor information may be used to adjust display color. For example,ambient light color information may be used by control circuitry 16 tochange the color cast of display 14 in response to a change in the colorenvironment of device 10 from warm indoor lighting to cool outdoorlighting conditions. Ambient light sensor information can also be usedin taking other suitable actions such as adjusting shading, texture, orother on-screen effects for objects on display 14, can be used inotherwise controlling the rendering of electronic content on display 14(e.g., adjusting the way in which electronic content such as text,graphics, animation, video, images, and other content is displayed), orcan be used in controlling other device functions during the operationof device 10. Illustrative arrangements in which display characteristicssuch as display brightness and display color (color cast) are changed inresponse to ambient light sensor information are sometimes be describedherein as an example.

One or more orientation sensors such as orientation sensors 22 may beused in monitoring the orientation of device 10 relative to the Earth.Information from an orientation sensor in device 10 may be used to helpdetermine the way in which a user of device 10 is holding device 10 andmay therefore be used to help assess whether a user's fingers areblocking sensors such as ambient light sensors 20.

Proximity sensors 24 may include one or more light-based proximitysensors. A light-based proximity sensor may include a light source suchas an infrared light-emitting diode and may include a light detectorsuch as a photodetector that is sensitive to infrared light. This typeof proximity sensor may produce a low output when no external objectsare in the vicinity of the detector. When a user's finger or otherexternal object is in the vicinity of the proximity sensor, emittedlight from the proximity sensor may be reflected into the light detectorfrom the external object and measured, producing a high output. Device10 can evaluate the size of the output signal from the light detector ofthe proximity sensor to determine whether or not an external object suchas the finger of a user is in the vicinity of the proximity sensor anddevice 10.

Touch sensors 26 may be provided as part of display 14, as part of atrack pad, or as stand-alone components. Touch sensors 26 may be basedon capacitive touch sensor technology or other touch sensor technology(acoustic touch, light-based touch, force-based touch, etc.). In anillustrative scenario, touch sensors 26 include capacitive touchsensors. A capacitive touch sensor has capacitive touch sensorelectrodes. When a user's finger or other external object contacts thetouch sensor electrodes, changes in capacitance can be measured (i.e., atouch event can be confirmed).

Force sensors 28 may include capacitive force sensors that measure forceby detecting changes in capacitance as force sensor electrodes aredeflected, may include resistive force sensor structures that changeresistance in response to applied force, may include strain gauges, mayinclude piezoelectric materials, or may contain other materials andstructures that measure applied force. Force sensors 28 may be used todetermine when a user's finger or other external objects are pressingagainst portions of device 10.

Image sensors 30 may be semiconductor integrated circuits that containarrays of image sensor pixels for capturing digital images. Focusinglenses may be used to focus images on image sensors 30 (i.e., sensors 30may serve as cameras in device 10). With one illustrative arrangement,image sensors 30 include a front image sensor (front camera) that facesoutwardly from a front face of device 10 and include a rear image sensor(rear camera) that faces outwardly from a rear face of device 10. Theremay be one image sensor, two image sensor, three image sensors, or anyother suitable number of image sensors in device 10. The image sensorsmay be used to capture full digital images of a scene and may, ifdesired, be used to capture ambient light data (e.g., by using a subsetof the image sensor pixels in each image sensor, by processing some orall of the image pixel data in a full frame of captured image data,and/or by using ambient light detector devices that are integrated ontoa common die with an array of image sensor pixels). Data from imagesensors 30 that is indicative of ambient lighting conditions arounddevice 10 and that does not represent an image of a scene may sometimesbe referred to as image sensor ambient light reading data.

If desired, sensors 18 may include other sensors such as a magneticsensor, a temperature sensor, a pressure sensor, a microphone or othersound sensor, or other sensors. Output data from these sensors may beprocessed by control circuitry 16 in conjunction with information fromsensors 20, 22, 24, 26, 28, and 30.

A perspective view of a portion of an illustrative electronic device isshown in FIG. 2. In the example of FIG. 2, device 10 includes a displaysuch as display 14 mounted in housing 32. Housing 32, which maysometimes be referred to as an enclosure or case, may be formed ofplastic, glass, ceramics, fiber composites, metal (e.g., stainlesssteel, aluminum, etc.), other suitable materials, or a combination ofany two or more of these materials. Housing 32 may be formed using aunibody configuration in which some or all of housing 32 is machined ormolded as a single structure or may be formed using multiple structures(e.g., an internal frame structure, one or more structures that formexterior housing surfaces, etc.).

Display 14 may be protected using a display cover layer such as a layerof transparent glass, clear plastic, sapphire, or other clear layer.Openings may be formed in the display cover layer. For example, anopening may be formed in the display cover layer to accommodate a buttonsuch as button 34, an opening may be formed for a speaker port, andopenings may be formed for other components. Openings may be formed inhousing 32 to form communications ports (e.g., an audio jack port, adigital data port, etc.), to form openings for buttons, etc.

Display 14 may include an array of display pixels formed from liquidcrystal display (LCD) components, an array of electrophoretic pixels, anarray of plasma pixels, an array of organic light-emitting diode pixelsor other light-emitting diodes, an array of electrowetting pixels, orpixels based on other display technologies. The array of pixels ofdisplay 14 forms an active area AA. Active area AA is used to displayimages for a user of device 10. Active area AA may be rectangular or mayhave other suitable shapes. Inactive border area IA may run along one ormore edges of active area AA. Inactive border area IA may containcircuits, signal lines, and other structures that do not emit light forforming images.

To hide inactive circuitry and other components in border area IA fromview by a user of device 10, the underside of the outermost layer ofdisplay 14 (e.g., the display cover layer or other display layer) and/orother layers of display 14 may be coated with an opaque masking materialsuch as a layer of black ink. Optical components (e.g., a camera, alight-based proximity sensor, ambient light sensors, status indicatorlight-emitting diodes, camera flash light-emitting diodes, etc.) may bemounted under inactive border area IA. One or more light-transmittingregions (sometimes referred to as windows, light-transmitting windows,or optical component windows) may be formed in the opaque masking layerof IA to accommodate the optical components. The windows may be formedfrom openings in the opaque masking layer and may, if desired, includeinks or other materials within the openings (e.g., aninfrared-transparent and visible-light-blocking layer for a proximitysensor that operates using infrared light and other layers with desiredspectral transmittance properties).

If desired, light-based components may also be mounted in other portionsof device 10 (e.g., locations where light is received through openingsin housing 32, portions of device 10 where light is received throughtransparent portions of display 14 in active area AA, etc.). In general,windows (light passageways) for optical components may be formed on therear surface of housing 32, on the sidewalls of housing 32, on displaycover layer of display 14 (e.g., in active area AA and/or inactiveregion IA), at the corners of inactive area IA, along the edges ofdevice 10, or elsewhere in device 10. In the illustrative configurationof FIG. 2, device 10 includes color ambient light sensors 20 (FIG. 1)mounted within housing 32 in alignment with ambient light sensor windows36 at the upper left and upper right corners of inactive area IA ofdisplay 14 and includes an image sensor 30 (FIG. 1) mounted withinhousing 32 in alignment with front camera window 38 between windows 36in the middle of the portion of inactive area IA that runs along theupper edge of display 14 (i.e., the edge of display 14 opposing the edgeat which button 34 is located). If desired, ambient light sensor windowsmay be located in the lower left and lower right corners of display 14or elsewhere in device 10 and/or additional front-facing camera windowsmay be formed in device 10. The example of FIG. 2 is merelyillustrative. As shown in the rear perspective view of device 10, device10 may also have one or more rear-facing camera windows such as rearcamera window 38 in a middle portion of the rear wall of housing 32along the upper edge of housing 32.

A cross-sectional side view of a portion of device 10 taken along line40 and viewed in direction 42 of FIG. 2 is shown in FIG. 4. As shown inFIG. 4, color ambient light sensor 20 may be mounted within housing 32of device 10 (i.e., in the interior of device 10) in alignment withwindow 36. Window 36 may be formed in inactive area IA of display 14.Display 14 may have a transparent planar member such as display coverlayer 44 (e.g., a layer of clear plastic, glass, sapphire, or othertransparent material(s)). In active area AA, display 14 may includedisplay layers 54 that form an array of pixels 56 for displaying imagesfor a user. Display cover layer 44 may overlap the array of pixels 56 inactive area AA.

To hide internal components in display 14 from view, the inner surfaceof display cover layer 44 in inactive area IA may have an opaque coatinglayer such as opaque masking layer 46. Window 36 may be formed withinopaque masking layer 46. Window 36 may, for example, be formed from acircular or rectangular opening in layer 46 that is aligned with ambientlight sensor 20. Camera window 38 of FIG. 2 may also be formed from anopening in opaque masking layer 46. If desired, ambient light sensorwindows such as window 36 may include coatings that filter incominglight (e.g., coatings that block infrared light, that block ultravioletlight, that partially block visible light, etc.).

During operation of device 10, color ambient light sensor 20 may be usedto make measurements on ambient lighting conditions in the vicinity ofdevice 10. Control circuitry 16 of device 10 can use ambient lightinformation to make adjustments to display 14 or to take other suitableactions. As shown in FIG. 4, ambient light may be generated by lightsources such as light source 50. Light source 50 may be the sun, a lamp,a light-emitting diode light bulb, or other suitable source of lighting.

Light source 50 may produce light 52. In some situations, light 52 maypass directly to color ambient light sensor 20 through window 36. Inother situations, light 52 may reflect off an external object in thevicinity of window 36 such as object 68 or may pass through a user'sfinger or other body part, as shown by finger 58 of FIG. 4. When light52 reflects off of external objects or passes through finger 58, light52 may obtain a color cast. For example, light 52 that passes throughfinger 58 may become reddish or light that reflects from a coloredobject may become unexpectedly warm or cold. The presence of externalobjects such as finger 58 may also block incoming light. If care is nottaken to account for the influence of external objects such as object 68and finger 58 in the path of ambient light 52, information on theintensity and color of light 52 that is gathered using color lightsensor 20 may not accurately reflect the actual ambient lightingconditions of device 10.

If desired, data from multiple color ambient light sensors 20 and/ordata from other sources (e.g., data from sensors 18 and other dataassociated with the operation of device 10) may be used to helpdetermine whether ambient light measurements by color ambient lightsensors 20 are reliable. In response to producing reliable color ambientlight sensor data (i.e., reliable ambient light intensity data andambient light color data), device 10 can take appropriate actions suchas adjusting the brightness and color of display 14. In response todetermining that color ambient light sensor information from colorambient light sensors 20 is not reliable, device 10 can gather new colorambient light sensor readings, access historical color ambient lightsensor readings, and/or may gather and process additional sensor data toproduce accurate color ambient light sensor data. For example, device 10can make color ambient light sensor measurements with multiple colorambient light sensors 20 and can process these measurements to determinewhether the gathered color ambient light sensor information is reliable.Device 10 can also use image sensor measurements, orientation sensormeasurements, and other input to help determine whether or not gatheredambient light sensor readings are reliable and/or to process ambientlight readings to produce reliable ambient light information for use bycontrol circuitry 16.

If desired, sensors may be used to measure when finger 58 or otherexternal objects are in the vicinity of window 36 and may therefore beimpairing the accuracy of color ambient light sensor 20. Consider, as anexample, the top view of a portion of display cover layer 44 in thevicinity of window 36 in FIG. 5. In the example of FIG. 5, a capacitivetouch sensor 26 has been incorporated into device 10 that has acapacitive touch sensor electrode 26E. Capacitive touch sensor electrode26E may be formed from a transparent material such as indium tin oxide(e.g., a transparent material that allows light 52 to pass throughwindow 36) and/or may be formed from an opaque material such as metalthat surrounds window 36. When a user's finger blocks window 36,readings from capacitive touch sensor 26 will detect the presence of theuser's finger and can alert control circuitry 16 that the readings beingmade by color ambient light sensor 20 under window 36 are not reliable.In addition to or instead of using a touch sensor such as capacitivetouch sensor 26 of FIG. 5, device 10 may include components such aslight-based proximity sensor 24. Proximity sensor 24 may have a lightsource such as infrared light-emitting diode 24E and a correspondinginfrared light detector 24D. When infrared light that is emitted bylight-emitting diode 24E is detected by light detector 24D, controlcircuitry 16 can conclude that a user's finger such as finger 58 orother external object with the potential to affect the intensity and/orcolor of light 52 that is being measured by color ambient light sensor20 is present in the vicinity of window 36.

Each of color ambient light sensors 20 is located under a differentwindow 36 and therefore may be affected differently by nearby objects(e.g., user finger 58, external light-reflecting object 68, etc.). Forexample, a user may hold device 10 in an orientation in which button 34is on the upper edge of device 10 (sometimes referred to as an upsidedown orientation or menu button up orientation). In this orientation,the thumbs of the user may cover both sensors 20. Scenarios in whichonly a single one of sensors 20 or neither of sensors 20 is blocked arealso possible. In some scenarios, it may be possible to determinewhether the light readings from sensors 20 are reliable by processingdata from sensors 20 in the absence of other sensor data. In otherscenarios, it may be helpful to analyze data from additional sensors 18.The way in which sensor data from sensors 20 is processed may varydepending on the usage scenario for device 10.

A flow chart of illustrative operations involved in gathering and usingcolor ambient light sensor measurements during the operation of device10 is shown in FIG. 6. In the illustrative example of FIG. 6, colorambient light sensor measurements are gathered from two color ambientlight sensors 20 and are processed by control circuitry 16 based solelyon the information available from sensors 20. In general, any suitablenumber of color ambient light sensors 20 may be used in gatheringambient light sensor information. The use of two ambient light sensorsto gather information is sometimes described herein as an example.

At step 70, control circuitry 16 may use color ambient light sensors 20to gather light intensity information on ambient light 52 and to gatherlight color information on ambient light 52. Color information (i.e.,color ambient light sensor color data) may be gathered as colorcoordinates, correlated color temperature (CCT) readings, or using othersuitable color sensing parameters. A first of sensors 20 may gather afirst ambient light intensity reading and a first ambient light colorreading. A second of sensors 20 may gather a second ambient lightintensity reading and a second ambient color reading. During theoperations of step 70, the intensity and color readings may beprocessed. For example, the intensity readings may be compared to eachother and/or to predetermined intensity values (e.g., threshold values).Similarly, the color readings may be compared to each other and/or topredetermined color values. These comparisons may reveal whether theintensity measured with the first sensor is similar to the intensitymeasured with the second sensor and may reveal whether the colormeasured with the first sensor is similar to the color measured with thesecond sensor. Intensity and color measurements may be said to besimilar to each other if they are within a predefined threshold amountof each other or satisfy other suitable similarity criteria and mayotherwise be said to be dissimilar.

The processing operations of step 70 may be used to determine how toprocess the intensity and color readings from sensors 20 to produceaccurate ambient light intensity and color information for use bycontrol circuitry 16 in adjusting display brightness and color or takingother suitable action. If, as an example, it is determined during step70 that the ambient light intensity readings and color readings from thefirst and second ambient light sensors 20 are similar to each other,control circuitry 16 may process the ambient light sensor data from thefirst and second sensors using the operations of step 72. At step 72,control circuitry 16 may, for example, compute the mean of the measuredlight intensities and the mean of the measured colors from the intensityand color data. The computed mean intensity may serve as the ambientlight sensor intensity value that control circuitry 16 uses to controldevice 10 and the computed mean color (e.g., mean color coordinates,mean correlated color temperature, etc.) may serve as the ambient lightsensor color value that control circuitry 16 uses to control device 10.

If, during the operations of step 70, it is determined that the measuredlight intensities from the first and second ambient light sensors aredissimilar and that the measured colors are similar, the sensor readingsmay be processed using the operations of step 74. During step 74,control circuitry 16 may discard the sensor readings from the ambientlight sensor 20 with the smaller of the two measured light intensitiesand may retain the sensor readings (color and intensity) from theambient light sensor 20 with the larger of the two measured lightintensities.

If, during the operations of step 70, it is determined that the measuredlight intensities from the first and second ambient light sensors aresimilar and that the measured colors are dissimilar, the sensor readingsmay be processed using the operations of step 76. During step 76,control circuitry 16 may compute the mean of the measured lightintensities from the first and second ambient light sensors. Controlcircuitry 16 may also identify a predetermined default ambient lightcolor (e.g., a predetermined target correlated color temperature such as6500 K, which may be associated with average daylight (D65) or apredetermined target set of color coordinates such as the D65 colorcoordinates). Control circuitry 16 may then select the predeterminedcolor, may select the sensor color value that is closes to apredetermined target color value (e.g., D65), may compute a mean of themeasured colors from the first and second ambient light sensors, mayselect a maximum or minimum of the color values, or may perform otherprocessing operations to select an appropriate color value to use as theambient light sensor color value that control circuitry 16 uses tocontrol device 10. The ambient light sensor intensity may be set to amean (or max, min, or other suitable function) of both sensor intensityreadings.

If, during the operations of step 70, it is determined that the measuredlight intensities from the first and second ambient light sensors aredissimilar and that the measured colors are dissimilar, the sensorreadings may be processed using the operations of step 78. During step78, control circuitry 16 may discard the sensor readings from theambient light sensor 20 with the smaller of the two measured lightintensities and may retain the sensor readings (color and intensity)from the ambient light sensor 20 with the larger of the two measuredlight intensities.

During processing operations (e.g., comparison operations in step 70and/or operations associated with steps 72, 74, 76, and/or 78), sensorhistory data and/or predetermined performance criteria may be used indetermining how to select appropriate intensity and/or color values. Forexample, sensor history information may be used to determine whetherrecently acquired sensor data from a sensor is too noisy, is abnormallyconstant, is too high or too low, or is otherwise likely to beassociated with a damaged sensor. If sensor damage criteria such asthese are satisfied by comparison of the sensor data to predeterminedcriteria and/or historical data, it may be concluded that associatedsensor values from a sensor are abnormal and not to be trusted. Controlcircuitry 16 can then discard the abnormal sensor values or the abnormalsensor values may be assigned low weighting factors. If the sensorappears to be permanently affected (e.g., by comparison of sensor datato historical data, predetermined performance criteria, or other damagedsensor criteria), sensor data can be permanently discarded (e.g., untilthe sensor can be repaired and the system reset).

At step 80, control circuitry 16 may take suitable actions based on theambient light sensor intensity and color values that have been obtainedby gathering and processing the ambient light sensor data from ambientlight sensors 20. For example, if ambient light intensity is low, thebrightness of display 14 may be lowered. If ambient light intensity ishigh, the brightness of display 14 may be raised. Ambient light colorinformation may also be used to make display adjustments. For example,if ambient lighting conditions are warm, the color of display 14 may beadjusted to exhibit a corresponding warmer color cast. In response todetection of cold lighting conditions, the color cast of display 14 maybe made correspondingly colder. Other actions may also be taken bycontrol circuitry 16 in response to measured ambient light intensity andcolor (e.g., camera adjustments, camera flash adjustments, adjustmentsto the texturing and shadowing of objects on display 14, adjustments tothe colors and intensities of text and graphical elements and/orbackground elements in displayed content, and/or other adjustments tothe operation of device 10). If desired, the actions taken at step 80may depend on the outcome of the sensor data processing operations ofstep 70. In situations in which sensor readings from different sensorsare dissimilar such as when dissimilar intensity and similar color isdetected (see, e.g., step 74), in which similar intensity and dissimilarcolor is detected (see, e.g., step 76), and in which dissimilarintensity and color is detected (see, e.g., step 78), the action takenduring the operations of step 80 may be more conservative than insituations in which the sensor readings from different sensors aresimilar (see, e.g., step 72). As an example, when sensor readings aredissimilar, smaller display brightness settings changes may be made ordisplay brightness changes may be made more slowly, color changes may besmaller or made more slowly, camera adjustments may be smaller or may beomitted, camera flash adjustments may be smaller or may be omitted, andless noticeable changes may be made to content on display 14 relative tothe actions taken when sensor readings are similar. In general,reductions in the amount of change and/or rate of change made tosettings associated with operating display 14 or any other suitabledisplay operating parameters may be made in response to reductions inthe amount of similarity between sensor readings. As illustrated by line82, operations may loop back to step 70 after step 80 so that additionalambient light sensor data may be gathered.

If desired, measured ambient light intensity from ambient light sensors20 may be used in determining how to process gathered ambient lightsensor readings. Consider, as an example, the arrangement of FIG. 7. Aswith the arrangement of FIG. 6, sensors readings may be gathered andcompared using ambient light sensors 20 (step 84). If the intensityand/or color readings of the first and second ambient light sensorsdiffer, appropriate action may be taken at step 86 to determineappropriate ambient light intensity and color values for use by controlcircuitry 16, as described in connection with steps 74, 76, and 78 ofFIG. 6.

In response to determining that both the intensity and color readingsfrom first and second ambient light sensors 20 are similar, controlcircuitry 16 may, at step 88, determine whether the measured lightintensity from the sensors is low (i.e., i.e., the mean of the measuredintensities below a predetermined threshold) or is high (i.e., the meanof the measured intensities is above the predetermined threshold).

In response to determining that the measured ambient light intensity ishigh, control circuitry 16 may set the ambient light intensity value tothe mean of the measured ambient light intensity of the first and secondambient light sensors 20 and may set the ambient light color value tothe mean of the measured ambient light color of the first and secondambient light sensors 20 (step 90).

If the measured ambient light intensity is low, control circuitry 16 maygather data from one or more of image sensors 30 at step 92. Forexample, control circuitry 92 may gather information from one or moresensor pixels in an image sensor associated with a front-facing cameraunder image sensor window 38 in inactive area IA of display 14. Thegathered image sensor data may be gathered from all of the pixels inimage sensor 30, from a subset of the image sensor pixels in imagesensor 30, and/or from non-image-pixel light detectors on the samesemiconductor die that forms image sensor 30. The image sensor data mayinclude ambient light intensity information and, if desired, ambientlight color information. The ambient light intensity informationgathered using the image sensor (e.g., from the front camera of device10) may be compared to a predetermined intensity value to determinewhether the intensity reading from the light sensor is high or low(above or below the predetermined intensity).

If the ambient light intensity reading from the image sensor is low likethe ambient light intensity readings from the ambient light sensors, itis unlikely that the ambient light sensors are blocked by the user'sfingers and is likely that device 10 is located in a dark environment.Accordingly, control circuitry 16 can conclude that the ambient lightsensor data from ambient light sensors 20 is reliable and can computethe means of the ambient light sensor intensity and color readings toproduce the ambient light sensor intensity and color values for controlcircuitry 16 to use in controlling the operation of device 10 (step 94).

If the ambient light intensity reading from image sensor 30 is high andtherefore differs from the ambient light intensity readings from ambientlight sensors 20, it is likely that the user's thumbs or other externalobjects are blocking ambient light sensors 20. Accordingly, controlcircuitry 16 can take appropriate remedial action at step 96. Forexample, control circuitry 16 can use a previous ambient light sensorreading from a stored ambient light sensor data history stored in memoryin circuitry 16 in place of the most current (and erroneous) lightsensor readings. As another example, control circuitry 16 can use theambient light readings gathered by the image sensor in place of theambient light readings gathered by ambient light sensors 20. As anotherexample, control circuitry 16 can use a weighted average technique orother processing technique to produce satisfactory ambient lightintensity and color values based on both ambient light sensor data fromsensors 20 and ambient light data from image sensor 30. Image sensors 30on the front and/or rear of device 10 may be used to supply intensityand color information to control circuitry 16. Sensors such as proximitysensor 24 and capacitive sensor 26 of FIG. 5 may also be used todetermine when sensors 20 have been blocked and are not producingreliable data.

The behavior of control circuitry 16 in determining which values to usefor the ambient light intensity and color information can vary overtime. For example, control circuitry 16 may not initially trust ambientlight sensor data from sensors 20 if the measured light intensity is lowand potentially corresponds to a blocked sensor, but may treat themeasured light intensity information as valid when sufficient time haspassed.

After taking the remedial actions of step 96 or after producing reliableambient light intensity and color values at steps 90 and 94, controlcircuitry 16 may take action based on the intensity and color values atstep 98 (e.g., display intensity may be adjusted, display color cast maybe adjusted, etc.). Processing may then loop back to step 84, asindicated by line 100.

In some arrangements, it may be desirable to use data from orientationsensor 22 to determine whether device 10 is being held in a right sideup or upside down configuration. It is more likely that sensors 20 alongthe top edge of device 10 are being blocked by a user's fingers whendevice 10 is being used in an upside down fashion.

Unusually colored ambient light readings may be indicative of blockedambient light sensors (e.g., because a user's finger may impart a colorcast to a light reading when the user's finger obscures some or all of alight sensor window). Accordingly, it may be desirable to acquireambient light data with an image sensor whenever abnormal color readingsare detected with ambient light sensors 20. If measured colorinformation deviates by more than a predetermined amount from the colorof known light sources (e.g., if the ambient light sensor colormeasurement deviates by more than a threshold value from the color gamutassociated with known light bulbs and other light sources), the ambientlight color value for control circuitry 16 to use in controlling device10 may be set to a predetermined (default) color value or additionalcolor measurements may be made in an attempt to acquire reliable colorand intensity information.

FIG. 8 is a diagram showing illustrative data sources that may be usedto provide sensor data and other data to an ambient light data processorroutine implemented on control circuitry 16. As shown in FIG. 8, controlcircuitry (e.g., ambient light sensor measurement processor 102) mayreceive information from a front-facing image sensor such as frontcamera 30A, from a rear-facing image sensor such as rear camera 30B,from proximity sensor 24, from capacitive touch sensor 26, from forcesensor 28 (e.g., a force sensor that measures force applied to all orsome of display 14 or other portions of the exterior of device 10 andhousing 32), from orientation sensor 22, and information from otherinput-output devices 104 and other circuitry in device 10 (e.g.,information indicating that button 34 of FIG. 2 is being pressed andthat a user's finger is therefore located on button 34, information onsoftware running on device 10 that helps identify the current operatingstate of device 10, etc.).

A flow chart of illustrative steps involved in operating device 10 whileusing information from sensors 18 and other information in device 10 ofthe type shown in FIG. 8 to determine how to process ambient lightsensor information from sensors 20 is shown in FIG. 9.

At step 106, control circuitry 16 may gather information from sensors18. The information may include measurements from ambient light sensorssuch as color ambient light sensors 20 and, if desired, additionalsensors 18. For example, in an arrangement of the type shown in FIG. 2,color ambient light sensor information may be gathered from a firstcolor ambient light sensor under window 36 on the upper left corner ofhousing 32 and from a second color ambient light sensor under window 36on the upper right corner of housing 32. These measurements may includeambient light intensity data and ambient light color data. Processingoperations such as comparisons of the readings of one of the colorambient light sensors to another and comparisons of the readings of eachcolor ambient light sensor to predetermined threshold values may beperformed to determine whether the ambient light data from one or bothsensors 20 is reliable or is unreliable (see, e.g., the operations ofFIGS. 6 and 7).

If the data analysis operations performed on the color ambient lightsensor measurements (and, if desired, additional sensor measurements) ofstep 106 indicate that the ambient light information from sensor(s) 20is reliable, operations may proceed to step 110, where suitable actionsmay be taken by control circuitry 16 based on the color ambient lightsensor information. Examples of actions that may be taken by device 10based on ambient light intensity and/or color information includeadjusting display brightness (e.g., increasing brightness when measuredambient light intensity values are high and decreasing brightness whenmeasured ambient light intensity values are low) and adjusting displaycolor cast such as adjusting display 14 so that display 14 rendersimages with a colder (bluer) appearance when device 10 is in a highcolor temperature environment such as outdoors environments and rendersimages with a warmer (yellower) appearance when device 10 is in a lowcolor temperature environment such as when device 10 is in an indoorsenvironment with warm interior lighting. Other actions may be takenbased on ambient light intensity and/or ambient light color, if desired.For example, control circuitry 16 can adjust the appearance of objectson display 14, can adjust the shading and texture of on-screen content,can change the operating mode of a book reading application or othersoftware running on device 10, etc.

If the data analysis operations performed on the color ambient lightsensor measurements (and, if desired, additional sensor measurements) ofstep 106 indicate that the ambient light sensor (ALS) information fromsensor(s) 20 is unreliable, operations may loop back to step 106 asindicated by line 112, so that additional information may be gatheredfrom sensors 20, sensors 18, and/or other sources of information on theoperating environment and operating status of device 10. The additionalsensor information that is gathered may include, for example,information from the data sources shown in FIG. 8 (e.g., one or more,two or more, or three or more, or four or more sources of data such assensors 30A, 30B, 26, 28, 22, 24, and other input-output devices 104).The additional information that is gathered may include, for example,intensity and/or color information on ambient light that is measuredusing a front-facing camera behind window 38 (FIG. 2). The front-facingcamera may not be blocked by a user's fingers even when both of sensors20 are blocked by the user's fingers, so examination of data from sensor30A may help reveal whether image sensors 20 are both blocked. Theadditional information that is gathered may also include informationfrom capacitive touch sensor(s) 26 and/or proximity sensor(s) 24 thatmay reveal whether a user's finger or other external object is blockingeither of sensors 20. Force sensor information from force sensor 28 mayreveal where a user's fingers are located (i.e., where force is beingapplied to a portion of display 14, etc.), which may, in turn, revealwhether sensors 20 are being blocked by the user's fingers. Orientationsensor 22 may reveal operational status information such as whetherdevice 10 is being used in a menu button up mode, a menu button to theside mode, or a menu button down mode. This orientation information may,in turn, reveal whether it is likely that user's fingers are blockingboth of sensors 20 (which is most likely when device 10 is in a menubutton up orientation). Information on the mode of operation of device10 and/or other information on the status and operating environment mayalso be gathered from other input-output devices 104. After gatheringadditional information from sensors 18 and other sources in this way,control circuitry 16 may process the information from sensors 20,sensors 18, and/or other devices 104 at step 108 to help producereliable ambient light data. The processing operations may involvecomparisons of sensor readings and other data to current readings (e.g.,comparisons of readings of one ambient light sensor 20 to another,comparisons of ambient light readings from ambient light sensor 20 toambient light readings made using an image sensor 30, etc.) and/or mayinvolve comparisons of sensor readings and other data to historicalvalues. Historical sensor data and other information may be maintainedin storage in control circuitry 16.

Reliable ambient light information that is produced during theprocessing operations of step 108 may be produced by selecting theambient light readings from a given one of sensors 20, by calculating amean value or otherwise processing information from both of sensors 20,by using ambient light information from an image sensor or other sensor18 in lieu of ambient light information from sensors 20 or incombination with ambient light information from sensors 20, or byotherwise processing information from ambient light sensor(s) 20,sensors 18, and/or other devices 104 to produce reliable information onambient light intensity and/or ambient light color. Following productionof reliable ambient light information, control circuitry 16 may takesuitable action at step 110 before looping back to step 106. If theprocessing operations of step 108 are unsuccessful at producing reliableambient light information, operations may loop back to step 106 withouttaking actions at step 110 so that additional sensor measurements may begathered.

The foregoing is merely illustrative and various modifications can bemade by those skilled in the art without departing from the scope andspirit of the described embodiments. The foregoing embodiments may beimplemented individually or in any combination.

What is claimed is:
 1. An electronic device that is exposed to ambientlight, comprising: a housing; control circuitry in the housing; firstand second color ambient light sensors; an additional sensor; and adisplay, wherein the control circuitry adjusts the display based oninformation from the first and second color ambient light sensors andthe additional sensor and wherein the control circuitry is configured toadjust a color cast of the display based on ambient light colorinformation from the color ambient light sensors.
 2. The electronicdevice defined in claim 1 wherein the additional sensor comprises animage sensor.
 3. The electronic device defined in claim 2 wherein thehousing has front and rear faces, wherein the display is mounted on thefront face, and wherein the display has light-transmitting windows in aninactive portion of the display.
 4. The electronic device defined inclaim 3 wherein the light-transmitting windows include first and secondlight-transmitting windows through which ambient light passesrespectively to the first and second ambient light sensors.
 5. Theelectronic device defined in claim 4 wherein the light-transmittingwindows include a third light-transmitting window that is locatedbetween the first and second light-transmitting windows and whereinambient light passes to the image sensor through the thirdlight-transmitting window.
 6. The electronic device defined in claim 1wherein the additional sensor comprises a capacitive touch sensor havingan electrode that monitors whether an object is blocking the first colorambient light sensor.
 7. The electronic device defined in claim 1wherein the additional sensor comprises a light-based proximity sensoradjacent to the first color ambient light sensor that monitors whetheran object is blocking the first color ambient light sensor.
 8. Theelectronic device defined in claim 1 wherein the additional sensorcomprises a force sensor.
 9. The electronic device defined in claim 1wherein the additional sensor comprises an orientation sensor.
 10. Theelectronic device defined in claim 1 wherein the control circuitry isconfigured to adjust the display by adjusting display brightness basedon ambient light intensity information from the first and second colorambient light sensors.
 11. The electronic device defined in claim 1wherein the control circuitry is configured to adjust the color castbased on ambient light color information produced by computing a mean ofan ambient light color measurement from the first color ambient lightsensor and an ambient light color measurement from the second colorambient light sensor.
 12. The electronic device defined in claim 1wherein the control circuitry is configured to maintain a history ofambient light intensity and color measurements from the first and secondcolor ambient light sensors and is configured to adjust the displaybased at least partly on the history.
 13. The electronic device definedin claim 1 wherein the control circuitry is configured to maintain ahistory of ambient light intensity and color measurements from the firstand second color ambient light sensors and is configured to discardambient light sensor intensity and color information from at least agiven one of the first and second color ambient light sensors when it isdetermined from a comparison between the ambient light sensor intensityand color information and the history of ambient light intensity andcolor measurements that the ambient light sensor intensity and colorinformation from the given one of first and second color ambient lightsensors is not to be trusted.
 14. The electronic device defined in claim1 wherein the control circuitry is configured to determine how much toadjust the display based at least partly on comparing ambient lightsensor readings from the first color ambient light sensor to ambientlight sensor readings from the second color ambient light sensor. 15.The electronic device defined in claim 1 wherein the control circuitryis configured to determine whether to discard data from the first andsecond color ambient light sensors by comparing data from the first andsecond color ambient light sensors to damaged sensor criteria.
 16. Amethod of adjusting a display in an electronic device having first andsecond color ambient light sensors and having control circuitry,comprising: with the control circuitry, gathering ambient lightmeasurements from the first and second color ambient light sensors; withthe control circuitry, processing the ambient light measurements fromthe first and second color ambient light sensors to produce ambientlight color information; and with the control circuitry, adjusting acolor cast of the display based on the ambient light color information.17. The method defined in claim 16 wherein the electronic device furthercomprises an image sensor and wherein processing the ambient lightmeasurements comprises processing both the ambient light measurementsfrom the first and second color ambient light sensors and measurementsfrom the image sensor to produce the ambient light color information.18. The method defined in claim 16 wherein the electronic device furthercomprises a touch sensor and wherein processing the ambient lightmeasurements comprises using ambient light measurements from the secondcolor ambient light sensor and not from the first color ambient lightsensor in response to detecting with the touch sensor that the firstambient light sensor is blocked.
 19. The method defined in claim 16wherein electronic device further comprises an orientation sensor andwherein processing the ambient light measurements from the first andsecond color ambient light sensors comprises using orientationinformation from the orientation sensor to determine whether the firstand second color ambient light sensors have been blocked by externalobjects.
 20. An electronic device, comprising: a housing; a displaymounted in the housing; a color ambient light sensor that makes ambientlight intensity measurements and ambient light color measurements; anadditional sensor that produces additional sensor data; and controlcircuitry that is configured to adjust display intensity and displaycolor cast for the display based on ambient light information producedby processing the ambient light intensity measurements, the ambientlight color measurements, and the additional sensor data, wherein thedisplay has an active area that displays images and an inactive areathat borders the active area, wherein the color ambient light sensor ismounted under a first window in the inactive area, wherein theadditional sensor is mounted under a second window in the inactive area,and wherein the additional sensor comprises a sensor selected from thegroup consisting of: a camera, a touch sensor that monitors whether thecolor ambient light sensor is blocked, an orientation sensor, a forcesensor, and a light-based proximity sensor.